Group III Nitride Enhancement-Mode HEMT with Composite Barrier Layer
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Solution Overview
Problem
Conventional group III nitride HEMTs based on AlGaN/AlN/GaN heterojunctions are depletion-mode, requiring complex and costly negative polarity gate drive circuits, and suffer from reliability issues due to low barrier height and electric leakage, making them unsuitable for commercial applications.
Innovation Solution
A group III nitride enhancement-mode HEMT with a composite barrier layer structure, featuring a high-Al-component barrier layer close to the channel and a low-Al-component barrier layer above, utilizing a high selectivity etching process to achieve precise recessed gate preparation, thereby improving threshold voltage and reducing electric leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low-Al-component thin-barrier-layer structure is used in the gate region, then the device can be manufactured with simpler processes, but the barrier height is low causing increased electric leakage and reduced gate threshold voltage swing
Solution Approach 1:
The barrier layer is divided into multiple segments with different Al components: a first barrier layer with lower Al component (e.g., Al0.15Ga0.85N) and a second barrier layer with higher Al component (e.g., Al0.30Ga0.70N). This segmentation allows the lower layer to provide good lattice matching and the upper layer to provide high barrier height, resolving the contradiction between manufacturing simplicity and device reliability.
Solution Approach 2:
Different regions of the barrier layer are assigned different Al components to fulfill different functions. The first barrier layer closer to the channel provides lattice matching and strain control, while the second barrier layer provides high barrier height to reduce leakage. This local quality differentiation simultaneously achieves manufacturing feasibility and device performance.
2Reliability
If a high-Al-component or thick barrier layer is used to improve normally-off performance, then the forward threshold voltage increases, but the carrier concentration in the channel is reduced leading to suboptimal output characteristics
Solution Approach 1:
The barrier layer is segmented into a first barrier layer with lower Al component that maintains good lattice matching and high carrier concentration for optimal output characteristics, and a second barrier layer with higher Al component that provides the necessary barrier height for normally-off performance. This segmentation resolves the contradiction between normally-off performance and output characteristics.
Solution Approach 2:
The Al component parameter is changed across the barrier layer thickness, with the first barrier layer having lower Al content (e.g., 15%) and the second barrier layer having higher Al content (e.g., 30%). This parameter gradient allows optimization of both threshold voltage and channel carrier concentration simultaneously.
3Reliability
If electrochemical corrosion and slow etching technologies are used for recessed gate preparation, then the threshold voltage and conduction characteristics can be optimized, but the process becomes complicated and difficult to control
Solution Approach 1:
The composite barrier layer structure is prepared in advance during epitaxial growth with specific Al component gradients. This preliminary action creates a structure that is naturally suitable for subsequent recessed gate etching, eliminating the need for complex electrochemical corrosion processes and simplifying the overall manufacturing process while maintaining device performance.
Solution Approach 2:
The etching selectivity is optimized by adjusting the Al component parameters of the barrier layers. The first barrier layer with lower Al content etches at a different rate than the second barrier layer with higher Al content, enabling precise recessed gate formation through controlled etching processes without requiring complex electrochemical steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composite barrier layer structure enables high-precision recessed gate preparation, enhances gate threshold voltage swing, and ensures uniformity of threshold voltage, making the device suitable for large-scale production and improving reliability.
Implementation Method 1
relative to the selected etching reagent, the first structure layer has higher etching resistance than the second structure layer
Implementation Method 2
due to the polarization effect of the group III nitride material system
Data Source
AI summary
A group III nitride enhancement-mode HEMT based on a composite barrier layer structure and a manufacturing method thereof are provided. The HEMT includes first and second semiconductors respectively serving as a channel layer and a barrier layer, a third semiconductor serving as a p-type layer, a source, a drain and a gate, wherein a recessed structure is formed in the region of the barrier layer corresponding to the gate, which is matched with the third semiconductor and the gate to form a p-type gate, and the second semiconductor includes first and second structure layers successively arranged on the first semiconductor; relative to the selected etching reagent, the first structure layer has higher etching resistance than the second structure layer.